Drive mechanism for a drug delivery device

ABSTRACT

A dose setting mechanism for a drug delivery device is disclosed. The mechanism comprises an outer housing and an inner housing having an external groove. The inner housing guides a driver having either a blocking or locking member disposed inside the driver that can lock a flexible tab to an internal groove during dose delivery in the inner housing such that the driver follows the path of the groove and to advance a spindle to move a cartridge bung. A dial sleeve is disposed between the outer and inner housing and is rotatably engaged with the inner housing.

BACKGROUND Field of the Present Patent Application

The present application is generally directed to dose setting mechanismsfor drug delivery devices. More particularly, the present application isgenerally directed to a dose setting mechanism comprising a stationaryinner housing having a driver positioned inside the inner housing andhaving a slidable locking or blocking member that locks a flexible tabto an internal groove in the inner housing such that the driver followsthe path of the groove during drug dispensing (injection).

Background

Pen type drug delivery devices have application where regular injectionby persons without formal medical training occurs. This may beincreasingly common among patients having diabetes where self-treatmentenables such patients to conduct effective management of their disease.

There are basically two types of pen type delivery devices: resettabledevices (i.e., reusable) and non-resettable (i.e., disposable). Thesetypes of pen delivery devices (so named because they often resemble anenlarged fountain pen) are generally comprised of three primaryelements: (i) a cartridge section that includes a cartridge oftencontained within a housing or holder; (ii) a needle assembly connectedto one end of the cartridge section; and (iii) a dosing sectionconnected to the other end of the cartridge section. A cartridge (oftenreferred to as an ampoule) typically includes a reservoir that is filledwith a medication (e.g., insulin), a movable rubber type bung or stopperlocated at one end of the cartridge reservoir, and a top having apierceable rubber seal located at the other, often necked-down, end. Acrimped annular metal band is typically used to hold the rubber seal inplace. While the cartridge housing may be typically made of plastic,cartridge reservoirs have historically been made of glass.

The needle assembly is typically a replaceable double-ended needleassembly. Before an injection, a replaceable double-ended needleassembly is attached to one end of the cartridge assembly, a dose isset, and then a dose is administered. Such removable needle assembliesmay be threaded onto, or pushed (i.e., snapped) onto the pierceable sealend of the cartridge assembly.

The dosing section or dose setting mechanism is typically the portion ofthe pen device that is used to set a dose. During an injection, aspindle contained within the dose setting mechanism presses against thebung or stopper of the cartridge. This force causes the medicationcontained within the cartridge to be injected through an attached needleassembly. After an injection, as generally recommended by most drugdelivery device and/or needle assembly manufacturers and suppliers, theneedle assembly is removed and discarded.

Different types of pen delivery devices, including disposable (i.e.,non-resettable) and reusable (i.e., resettable) varieties, have evolvedover the years. For example, disposable pen delivery devices aresupplied as self-contained devices. Such self-contained devices do nothave removable pre-filled cartridges. Rather, the pre-filled cartridgesmay not be removed and replaced from these devices without destroyingthe device itself. Consequently, such disposable devices need not have aresettable dose setting mechanism.

In contrast to typical disposable pen type devices, typical reusable pendelivery devices feature essentially two main reusable components: acartridge holder and a dose setting mechanism. After a cartridge isinserted into the cartridge holder, this cartridge holder is attached tothe dose setting mechanism. The user uses the dose setting mechanism toselect a dose. Before the user injects the set dose, a replaceabledouble-ended needle assembly is attached to the cartridge housing.

This needle assembly may be threaded onto or pushed onto (i.e., snappedonto) a distal end of the cartridge housing. In this manner, a doubleended needle mounted on the needle assembly penetrates through apierceable seal at a distal end of the cartridge. After an injection,the needle assembly is removed and discarded. After the insulin in thecartridge has been exhausted, the user detaches the cartridge housingfrom the dose setting mechanism. The user can then remove the emptycartridge from the cartridge retainer and replace the empty cartridgewith a new (filled) cartridge.

Aside from replacing the empty cartridge with a new cartridge, the usermust somehow prepare the dose setting mechanism for a new cartridge: thedose setting mechanism must be reset to a starting or initial position.For example, in certain typical resettable devices, in order to resetthe dose setting mechanism, the spindle that advances in a distaldirection during dose injection must somehow be retracted back into thedose setting mechanism. Certain known methods of retracting this spindleback into the dose setting mechanism to a restart or an initial positionare known in the art. As just one example, known reset mechanismsrequire a user to turn back or push back (retract) the spindle or someother portion of the dose setting mechanism.

Resetting of known dose setting mechanisms have certain perceiveddisadvantages. One perceived disadvantage is that the pen device userhas to disassemble the device to either remove an empty cartridge orsomehow reset the device. As such, another perceived disadvantage isthat such devices have a high number of parts and therefore such devicesare typically complicated from a manufacturing and from an assemblystandpoint. For example, certain typical resettable pen type devices arenot intuitive as to how a user must replace an empty cartridge and resetthe device. In addition, because such resettable devices use a largenumber of components parts, such resettable devices tend to be large andbulky, and therefore not easy to carry around or easy to conceal.

There is, therefore, a general need to take these disadvantagesassociated with resetting issues into consideration in the design anddevelopment of resettable drug delivery devices. Such desired drugdelivery devices would tend to reduce the number of component parts andalso tend to reduce manufacturing costs while also making the deviceless complex to assemble and manufacture. Such desired devices wouldalso tend to simplify the steps required for a user to reset a dosesetting mechanism while also making the device less complex and morecompact in size.

SUMMARY

According to an exemplary arrangement, my invention is directed to adrug delivery device having a driver locking feature comprising acartridge holder containing a cartridge of medicament connected to adose dialing assembly. The cartridge contains a bung or piston that isacted upon by a spindle during dose delivery. The dose dialing assemblycomprises an outer housing and an inner stationary housing, where theinner housing has at least one internal groove running along the axis ofthe inner surface. The assembly contains a driver positioned within theinner housing and a flexible tab that engages the internal groove toform a detent during dose dialing. Inside the driver is a blockingmember that can slide and lock the flexible tab in the groove duringdose dispensing such that the driver is forced to follow the path of thegroove. The flexible tab can be part of the driver, preferably locatednear the distal end of the driver, or it can be a stand-alone component.Preferably my invention comprises two or more flexible tabs. The tabscan be manufactured from any flexible material, preferably using amaterial that can form a detent with the groove in the inner housingduring dose setting and most preferably to provide both a tactile andaudile feedback to the user.

In another embodiment, the blocking member has an aperture that isaligned with the flexible tab when the blocking member is in anon-locked position and is misaligned with the flexible tab when in thelocked position. When misaligned, the flexible tab is locked in thegroove. The groove can be parallel to the axis of the inner housing orit can be helical. When the groove is parallel, the driver will notrotate during dose injection and when the groove is helical, the driverwill rotate following the path of the groove during dose injection.

My invention also relates to a method of setting and injecting a dose ofmedicament with a drug delivery device that comprises a first step wherea user holds a dosing assembly of an injection device as described aboveand rotates the driver in a first direction to set a dose. During dosesetting the driver rotates relative to the external and inner housingsand the flexible tab overrides the internal groove. Once the dose isset, the user pushes an injection button that is clutched to the driverto cause the driver to move distally in a second direction. This actionalso moves the blocking member in an axial distal direction to a lockedposition to engage the flexible tab causing it to non-releasably engagethe internal groove. This causes the driver to follow the path of thegroove while moving distally in the second direction and ultimatelyexpels medicament from the drug delivery device.

Yet another embodiment of my drug delivery device that has a drivesleeve lockout feature is one where there is a locking member slidablypositioned inside the driver that has an associated flexible tab thatengages the internal groove to form a detent during dose dialing. Whenin a locked position during dose dispensing the flexible tab is lockedin engagement with the groove such that the driver follows the path ofthe groove. The flexible member can engage the groove through anaperture in the driver and when in the locked position, the tab isbiased into the groove by the misaligned driver aperture.

Another embodiment is a method of setting and injecting a dose ofmedicament with an injection device having a driver lockout featurewhere rotation of the driver in the first direction during dose settingrelative to the housing causes the flexible tab associated with thelocking element to releasably engage and override the groove causing anaudible click. Once the dose is set the user pushes an injection buttonto inject a set dose that advances the driver in a second direction andmoves the locking member in an axial distal direction so that theflexible tab is locked in engagement with the groove. This causes thedriver to follow the path of the groove ultimately expelling medicamentfrom the drug delivery device.

In each of the embodiments described a dial sleeve is disposed betweenthe outer and inner housing and is rotatably engaged with an externalgroove of the inner housing. This engagement may include a nut that isrotatably fixed to the dose dial sleeve and threadedly engaged to theexternal groove on the inner housing. When setting a dose, the dialsleeve is rotated with respect to both the outer housing and the innerhousing. The dial sleeve is translated away in the proximal directionfrom both the outer housing and the inner housing. The locking orblocking members can be biased in the proximal direction during dosesetting so that the tabs form a detent. During the dose injection stepthe biasing member, preferably a spring, is overcome by the forceexerted when the user pushes the injection button.

These as well as other advantages of various aspects of the presentinvention will become apparent to those of ordinary skill in the art byreading the following detailed description, with appropriate referenceto the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments are described herein with reference to thedrawings, in which:

FIG. 1 illustrates an embodiment of a resettable drug delivery device;

FIG. 2 illustrates a cross sectional view of one embodiment of the drivemechanism to specifically illustrate the linear shape of the at leastone groove on the internal surface of the inner housing;

FIG. 3 illustrates a cross sectional view of one embodiment of the drivemechanism to specifically illustrate the helical shape of the at leastone groove on the internal surface of the inner housing;

FIG. 4 illustrates a cross sectional view of one embodiment of the drivemechanism illustrating the blocking member engaging two flexible tabs tolock them into the groove in the inner housing;

FIG. 5 is a close-up of the cross sectional view of one embodiment ofthe drive mechanism illustrated in FIG. 4 showing the blocking member ina non-locked position and two flexible tabs forming a detent with thegroove in the inner housing;

FIG. 6 is a close-up of the cross sectional view of one embodiment ofthe drive mechanism illustrated in FIG. 4 showing the blocking member ina locked position and two flexible tabs locked with the groove in theinner housing;

FIG. 7 is a perspective view of the driver of an alternative embodimentof the drive mechanism on our invention showing two flexible tabsprotruding through apertures in the driver during dose setting;

FIG. 8 is a perspective view of the locking member having three flexibletabs associated therewith at its distal end;

FIG. 9 is a close-up of the cross sectional view of an alternativeembodiment of the drive mechanism of our invention showing the lockingmember in an un-locked position and two flexible tabs forming a detentwith the groove; and

FIG. 10 is a close-up of the cross sectional view of an alternativeembodiment of the drive mechanism of our invention showing the lockingmember in a locked position and two flexible tabs locked with the groovein the inner housing.

DETAILED DESCRIPTION

Referring to FIG. 1, there is shown a drug delivery device 1 inaccordance with an exemplary arrangement. The drug delivery device 1comprises a housing having a first cartridge retaining part 2, and adose setting mechanism 4. The drug delivery device may be a resettabledrug delivery device (i.e., a reusable device) or alternatively anon-resettable drug delivery device (i.e., a non-reusable device). Afirst end of the cartridge retaining part 2 and a second end of the dosesetting mechanism 4 are secured together by connecting features. Fornon-resettable devices, these connecting features would be permanent andnon-reversible. For resettable devices, these connecting features wouldbe releasable.

In this illustrated arrangement, the cartridge housing 2 is securedwithin the second end of the dose setting mechanism 4. A removable cap(not shown) is releasably retained over a second end or distal end of acartridge retaining part or cartridge housing. The dose settingmechanism 4 comprises a dose dial grip 12 and a window or lens 14. Adose scale arrangement is viewable through the window or lens 14. To seta dose of medication contained within the drug delivery device 1, a userrotates the dose dial grip 12 such that a dialed dose will becomeviewable in the window or lens 14 by way of the dose scale arrangement.

FIG. 1 illustrates the medical delivery device 1 with the cover capremoved from a distal end 18 of the medical delivery device 1. Thisremoval exposes the cartridge housing 6. Preferably, a cartridge (notshown) from which a number of doses of a medicinal product may bedispensed, is provided in the cartridge housing 6. Preferably, thecartridge contains a type of medicament that can be administeredrelatively often, such as once or more times a day. One such medicamentis either long acting or short acting insulin or an insulin analog. Thecartridge comprises a bung or stopper that is retained near a second endor a proximal end of the cartridge. The medical delivery device alsocomprises a driver 7, preferably having at least two portions, 7 and 9(see FIG. 4), and a spindle 10 (see FIG. 9), that is in threadedengagement 15 with the distal portion of the driver 9.

The cartridge housing 6 has a distal end and a proximal end. Preferably,the distal end of the cartridge housing 6 comprises a hub 8 forattaching a removable needle assembly. However, other needle assemblyconnection mechanisms could also be used. If the drug delivery device 1comprises a resettable device, the cartridge proximal end is removablyconnected to the dose setting mechanism 4. In one preferred embodiment,the cartridge housing proximal end is removably connected to the dosesetting mechanism 4 via a bayonet connection. However, as those ofordinary skill in the art will recognize, other types of removableconnection methods such as threads, partial threads, ramps and detents,snap locks, snap fits, and luer locks may also be used.

As previously mentioned, the dose setting mechanism 4 of the drugdelivery device illustrated in FIG. 1 may be utilized as a reusable drugdelivery device. (i.e., a drug delivery device that can be reset) Wherethe drug delivery device 1 comprises a reusable drug delivery device,the cartridge is removable from the cartridge housing 6. The cartridgemay be removed from the device 1 without destroying the device 1 bymerely having the user disconnect the dose setting mechanism 4 from thecartridge housing 6.

In use, once the cap is removed, a user can attach a suitable needleassembly to the hub 8 provided at the distal end of the cartridgehousing 6. Such needle assembly may be, for example, screwed onto adistal end of the housing 6 or alternatively may be snapped onto thisdistal end. After use, the replaceable cap may be used to re-cover thecartridge housing 6. Preferably, the outer dimensions of the replaceablecap are similar or identical to the outer dimensions of the dose settingmechanism 4 so as to provide an impression of a unitary whole when thereplaceable cap is in position covering the cartridge housing 6 when thedevice is not in use.

FIG. 4 illustrates a perspective, cross sectional view of onearrangement of a dose setting mechanism 4. Those of skill in the artwill recognize that dose setting mechanism 4 may include a connectionmechanism for releasably connecting to a cartridge holder, like thecartridge holder 6 illustrated in FIG. 1. However, as those of ordinaryskill in the art will recognize, the dose setting mechanism may alsoinclude a permanent connection mechanism for permanently connecting to acartridge holder. The dose setting mechanism 4 comprises an outerhousing 17 containing a number (or dose dialing) sleeve 3, a stationaryinner housing 5, a connector 19, a proximal driver portion 7, a distaldriver portion 9, and a biasing member, preferably a compression spring13. A spindle 10 (see FIG. 10) may engage thread 15 inside the distaldriver 9 and that is connected to pressure plate 16 that abuts cartridgebung 20. In one arrangement, the spindle can be generally circular incross section however other arrangements and shapes may also be used.

Both the proximal and distal driver portions are positioned inside thestationary inner housing 5. The inner housing has at least one groove onits inner surface, most preferably a series or set of grooves runningalong the axis of the inner housing. FIGS. 2 and 3 show two preferreddesigns for the grooves, linear grooves 30 (FIG. 2) and helical grooves31 (FIG. 3). Returning to FIG. 4 the proximal driver has an associatedflexible tab 21. In the embodiment shown, there are two flexible tabsand two corresponding apertures 23 in blocking member 11 that allow theflexible tabs to flex into forming a detent with the grooves on theinner housing 5. This detent or clicker provides the user with anaudible and tactile feedback as a dose is set because the flexible taboverrides the grooves as the driver 7 is rotated outwardly (proximally)with the dial sleeve 3. This shown in FIG. 5. FIGS. 4 and 6 shows theblocking member 11 in its locked position, urged distally forward duringdose delivery, thus locking flexible tabs 21 into the grooves of theinner housing and ensuring that the driver follows the path of thegrooves.

During dose delivery, blocking member 11 is urged or slid distallycompressing biasing component 13, which during dose setting biases theblocking member proximally preventing the flexible tabs from lockingwith the grooves. This sliding distal movement of the locking memberduring dose delivery constrains the flexible tab 23 such that theproximal driver portion 7 is locked to the inner housing ensuring thatthe proximal driver 7 follows the path of the grooves in the innerhousing. The axial movement of the locking member 11 also causesconnector 19 to lock the distal driver portion 9 to proximal driver 7 toensure that the distal portion of the driver moves in the same directionas the proximal driver. The connector 19 can be fixed to the distaldriver as a separate component or can be an integral part of the distaldriver formed during the molding or machining of the distal driver. Theconnector is in a connected position relative to the proximal driverduring dose setting and dose delivery and is in an un-connected positionin a preferred embodiment when the device is designed to be resettable,as explained below in more detail. Both the distal and proximal driverportions 9 and 7 are preferably generally cylindrical.

In an alternative embodiment, as shown in FIGS. 7-10, the flexible tabsare associated with locking member 11′, preferably they are integral tothe distal end of the locking member. Alternatively, the flexible tabsmay be part of a separate component. FIG. 9 shows the locking member 11′in the un-locked proximal position during dose setting where theflexible tabs 21 are acting as a detent, riding in and out of thegrooves of the inner body as the driver and locking member are rotatedoutwardly. FIG. 10 shows the locking member 11′ in the locked positionthat occurs when the user pushes the injection button and urges thelocking member forward (distally). This forward sliding motion causesthe tabs to be locked into the grooves because the external surface ofthe driver acts as a blocking surface preventing the tabs fromdisengaging the grooves during dose delivery.

In normal use, the operation of the dose setting mechanism 4 occurs asfollows. To dial a dose in the arrangement illustrated in FIGS. 4-6, auser rotates the dose dial grip 12. The proximal driver 7, the distaldriver 9, the connector 10, the biasing element 13 and the number sleeve3 rotate along with the dose dial grip 12. The number sleeve 3 extendsin a proximal direction away from the housing 17. In this manner, thethread 15 of the distal driver 9 rotates over the spindle. At the limitof travel, a radial stop on the number sleeve 3 engages a stop providedon either the housing 17 or the inner housing 5 to prevent furthermovement. Rotation of the spindle is prevented because the thread 15 ofthe distal driver has the same lead as the external helical groove ofthe inner housing 5. A dose limiter 22, splined to the inner housing 5,may be included in a preferred embodiment and is advanced along thethread 23 of the distal driver by the rotation of the distal driver 9.As the driver rotates in the first direction (proximally) the flexibletabs override the grooves of the inner housing forming a detent.

When the desired dose has been dialed, the user may then dispense thedesired dose by depressing the proximal face of the dial grip 12. As theuser depresses the dial grip 12, this displaces a clutch (not shown),which ensures the dose dial sleeve and proximal driver move togetherduring dose setting, axially with respect to the number sleeve 3,causing the clutch to disengage. Once the clutch is disengaged, thelocking member will be urged forward to lock the flexible tabs into thegrooves of the inner housing causing the proximal driver to follow thepath of the groove. If the grooves are linear (straight), as shown inFIG. 2, the proximal driver will not rotate relative to the innerhousing. If the grooves are helical, as shown in FIG. 3, the proximaldriver will rotate relative to inner housing. The dose dial sleeve 3 andthe dial grip 12 are free to rotate back to the starting positionindependent of the movement of the proximal driver. Because the proximaldriver 7 is engaged with the distal driver 9 through the connector 19,the distal driver will move in the same direction along the same path asthe proximal driver.

The driver is prevented from rotating with respect to the main housing17 and inner housing 5 when the grooves in the inner housing arestraight and parallel to axis of the inner housing, but the driver willrotate and move axially if the grooves are helical. In either case, thelongitudinal axial movement of the drivers causes the spindle 10 torotate and thereby to advance the piston or bung 20 in the cartridge toexpel the dialed dose of medication through an attached needle assemblyreleasably connected to the distal end 8 of the cartridge holder 6.

In a preferred embodiment, after the drug delivery device has dispensedall of the medication contained in the cartridge, the user may wish toreplace the empty cartridge in the cartridge holder 6 with a newcartridge. The user must then also reset the dose setting mechanism 4:for example, the user must then retract or push the spindle back intothe dose setting mechanism 4. In order to retract the spindle of thearrangement shown in FIGS. 4-6, the distal portion and the proximalportion of the driver must be de-coupled from one another. The user maypush the spindle, which in turn urges the distal portion of the driverin the proximal direction compressing biasing component 13 thusdisengaging connector 19 from the proximal portion of the driver. Afterdecoupling, the distal driver portion will be free to rotate relative tothe proximal portion.

During a device resetting step, rotating the distal portion of thedriver achieves at least two results. First, as the distal portion ofthe driver rotates it will reset the axial position of the spindle withrespect to the dose setting mechanism 4 to a fully retracted position.Second, rotation of the distal portion of the driver will also axiallymove or reset dose limiter 22 to an initial or start position becausethe dose limiter is threadedly engaged to the outer threads 23 of thedistal driver and is splined to the groove on the inner surface of theinner housing. In this configuration, the dose limiter 22 is preventedfrom rotating but will move along the outer threads 23 of the distaldriver portion 9 as this portion is rotated during a resetting step.

Exemplary embodiments of the present invention have been described.Those skilled in the art will understand, however, that changes andmodifications may be made to these embodiments without departing fromthe true scope and spirit of the present invention, which is defined bythe claims.

1. A drug delivery device having a driver locking feature comprising, a.a cartridge holder configured to contain a cartridge of medicamentconnected to a dose dialing assembly, where the dose dialing assemblycomprises an outer housing and an inner stationary housing having atleast one internal groove on an inner surface; b. a driver positionedwithin the inner housing; c. a flexible tab that engages the internalgroove to form a detent during dose dialing; and d. a blocking memberslidably positioned inside the driver that locks the flexible tab intothe groove during dose dispensing such that the driver follows the pathof the groove.
 2. The drug delivery device of claim 1 where the flexibletab is an integral part of the driver.
 3. The drug delivery device ofclaim 1 where the driver contains at least two flexible tabs.
 4. Thedrug delivery device of claim 1 where the blocking member has anaperture that is aligned with the flexible tab when the blocking memberis in a non-locked position and is misaligned with the flexible tab whenin the locked position.
 5. The drug delivery device of claim 4 where theflexible tab is locked in the groove when the aperture is misaligned. 6.The drug delivery device of claim 1 where the groove is parallel to theaxis of the inner housing.
 7. The drug delivery device of claim 1 wherethe groove is helical along the axis of the inner housing.
 8. A methodof setting and expelling a dose of medicament with a drug deliverydevice, a. holding or providing a dosing assembly of an injectiondevice, where the dosing assembly comprises, i. an external housing andan internal housing having at least one internal groove; ii. a driverpositioned within the inner housing; iii. a flexible tab that engagesthe internal groove to form a detent during dose setting; and iv. ablocking member slidably positioned inside the driver that engages theflexible tab when in a locked position; b. rotating the driver in afirst direction during dose setting relative to the external and innerhousings whereby the flexible tab overrides the internal groove; c.pushing an injection button clutched to the driver to cause the driverto move distally in a second direction; d. moving the blocking member inan axial distal direction to a locked position and engaging the flexibletab causing the flexible tab to non-releasably engage the internalgroove; and e. expelling medicament from the drug delivery device. 9.The method of claim 8 wherein the internal groove is linear along theaxis of the inner housing and the second direction of the driver islinear distally.
 10. The method of claim 8 wherein the internal grooveis helical and the second direction of the driver is rotating distally.11. The method of claim 8 wherein the flexible tab causes an audibleclick when the driver is rotated in the first direction and providestactile feedback to a user.
 12. A drug delivery device having a drivesleeve lockout feature comprising, a. a cartridge holder containing acartridge of medicament connected to a dose dialing assembly, where thedose dialing assembly comprises an outer housing and an inner stationaryhousing having at least one internal groove on an inner surface; b. adriver positioned within the inner housing; and c. a locking memberslidably positioned inside the driver and having a flexible tab thatengages the internal groove to form a detent during dose dialing,wherein locking member has a locked position during dose dispensingwhere the flexible tab is irreversibly engaged with the groove such thatthe driver follows the path of the groove
 13. The drug delivery deviceof claim 12 where the driver has an aperture to receive the flexibletab.
 14. The drug delivery device of claim 13 where the aperture isaligned with the flexible tab during dose dialing and is misaligned withthe flexible tab during dose delivery.
 15. A method of setting andinjecting a dose of medicament with an injection device, a. holding adosing assembly of a drug delivery device, where the dosing assemblycomprises, i. a cartridge holder containing a cartridge of medicamentconnected to a dose dialing assembly, where the dose dialing assemblycomprises an outer housing and an inner stationary housing having atleast one internal groove on an inner surface; ii. a driver positionedwithin the inner housing; and iii. a locking member slidably positionedinside the driver and having a flexible tab that engages the internalgroove to form a detent during dose dialing, wherein the locking memberhas a locked position during dose dispensing; b. rotating the driver inthe first direction during dose setting relative to the housing wherebythe flexible tab releasably engages and overrides the groove causing anaudible click; c. pushing an injection button to inject a set dose; d.advancing the driver in a second direction; e. moving the locking memberin an axial distal direction so that the flexible tab is irreversiblyengaged with the groove such that the driver follows the path of thegroove; and f. expelling medicament from the drug delivery device. 16.The device of claim 15 wherein the groove is linear and the seconddirection of the driver is linear in the distal direction.
 17. Thedevice of claim 15 wherein the groove is helical and the seconddirection of the driver is rotational in the distal direction.
 18. Thedevice of claim 15 wherein the flexible tab causes a tactile feedback tothe user when the driver is rotated in the first direction.
 19. A dosesetting mechanism for a drug delivery device, said mechanism comprising:a. a proximal driver positioned inside a stationary inner housing havinga inner surface; b. a clicker formed between the proximal driver and theinner surface of the inner housing, where the clicker forms a detentwith at least one groove in the inner housing during dose setting and islocked with the inner housing during dose delivery; and c. a lockingmember that is axially slidable inside the proximal driver and thatengages the clicker during dose setting to lock the clicker into the atleast one groove in the inner housing.
 20. The dose setting mechanism ofclaim 19 further comprising a distal driver positioned inside the innerhousing having a connector for engaging the proximal driver during dosesetting and drug dispensing.
 21. The dose setting mechanism of claim 20further comprising a biasing member positioned between the proximaldriver and the connector.
 22. The dose setting mechanism of claim 1where the clicker has at least one flexible arm that engages the atleast one groove in the inner housing to form the detent during dosesetting.